PrepGo

AP Chemistry Practice Quiz: Properties of Photons

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

Test your understanding with short quizzes. This quiz has 9 questions to check your progress.

Question 1 of 9

When an atom absorbs a photon, how does the energy of the atom change?

All Questions (9)

When an atom absorbs a photon, how does the energy of the atom change?

A) It decreases by an amount equal to the photon's energy.

B) It increases by an amount equal to the photon's energy.

C) It remains exactly the same.

D) It doubles, regardless of the photon's energy.

Correct Answer: B

According to the provided content, when an atom or molecule absorbs a photon, its energy increases by an amount equal to the photon's energy. This is a direct application of the law of conservation of energy to electronic transitions.

An electronic transition in a molecule results in the emission of a photon. This indicates that the molecule has...

A) moved from a lower energy state to a higher energy state.

B) moved from a higher energy state to a lower energy state.

C) absorbed energy from its surroundings.

D) undergone a change in its chemical composition.

Correct Answer: B

The content states that when a molecule emits a photon, its energy decreases. This decrease corresponds to a transition from a higher initial energy state to a lower final energy state, with the energy difference being released as a photon.

According to Planck's equation, E = hν, what is the relationship between the energy of a photon and its frequency?

A) They are inversely proportional; as frequency increases, energy decreases.

B) They are directly proportional; as frequency increases, energy increases.

C) They are independent of each other.

D) Energy is proportional to the square of the frequency.

Correct Answer: B

Planck's equation, E = hν, shows that the energy (E) of a photon is the product of its frequency (ν) and Planck's constant (h). Since h is a constant, E is directly proportional to ν.

Based on the equation c = λν, if a photon has a very long wavelength (λ), what can be inferred about its frequency (ν)?

A) It has a very high frequency.

B) It has a very low frequency.

C) Its frequency is equal to the speed of light.

D) Its frequency cannot be determined from its wavelength.

Correct Answer: B

The equation c = λν relates the speed of light (c), a constant, to wavelength (λ) and frequency (ν). To keep the product c constant, if wavelength (λ) is large, the frequency (ν) must be small. This demonstrates an inverse relationship between wavelength and frequency.

The energy of a photon emitted during an electronic transition is precisely equal to...

A) the initial energy of the atom before the transition.

B) the final energy of the atom after the transition.

C) the sum of the initial and final energy states of the atom.

D) the difference in energy between the initial and final electronic states of the atom.

Correct Answer: D

The content explains that when an atom emits a photon, its energy decreases by an amount equal to the photon's energy. This means the photon's energy corresponds exactly to the energy difference between the higher-energy initial state and the lower-energy final state.

Which of the following expressions correctly combines the equations E = hν and c = λν to relate a photon's energy (E) directly to its wavelength (λ)?

A) E = hλ/c

B) E = cλ/h

C) E = hc/λ

D) E = h/(cλ)

Correct Answer: C

To relate energy to wavelength, first rearrange c = λν to solve for frequency: ν = c/λ. Then, substitute this expression for ν into Planck's equation: E = hν becomes E = h(c/λ), or E = hc/λ.

An atom absorbs a photon of light with a short wavelength. What can be concluded about the energy of this photon and the resulting transition?

A) The photon has low energy, causing a small increase in the atom's energy.

B) The photon has high energy, causing a large increase in the atom's energy.

C) The photon has low energy, causing a large decrease in the atom's energy.

D) The photon has high energy, causing a small decrease in the atom's energy.

Correct Answer: B

First, relate wavelength to energy. From c = λν, a short wavelength (λ) implies a high frequency (ν). From E = hν, a high frequency (ν) implies high energy (E). Second, the content states that when a photon is absorbed, the atom's energy increases by the photon's energy. Therefore, a high-energy photon causes a large increase in the atom's energy.

Consider two photons of electromagnetic radiation. Photon A has a frequency twice as high as Photon B. What is the relationship between their energies?

A) The energy of Photon A is half the energy of Photon B.

B) The energy of Photon A is equal to the energy of Photon B.

C) The energy of Photon A is twice the energy of Photon B.

D) The energy of Photon A is four times the energy of Photon B.

Correct Answer: C

According to Planck's equation, E = hν, the energy of a photon is directly proportional to its frequency. If Photon A has a frequency (ν_A) that is twice the frequency of Photon B (ν_B), so ν_A = 2ν_B, then its energy (E_A) will be E_A = h(2ν_B) = 2(hν_B) = 2E_B.

An atom undergoes an electronic transition, and its energy decreases by 4.0 x 10⁻¹⁹ J. Which of the following describes the photon involved in this process?

A) A photon with an energy of 4.0 x 10⁻¹⁹ J was absorbed by the atom.

B) A photon with an energy of 4.0 x 10⁻¹⁹ J was emitted by the atom.

C) A photon with a frequency of 4.0 x 10⁻¹⁹ Hz was absorbed by the atom.

D) A photon with a wavelength of 4.0 x 10⁻¹⁹ m was emitted by the atom.

Correct Answer: B

The content states that when an atom's energy decreases, it emits a photon. The energy of this emitted photon is equal to the amount of energy lost by the atom. Therefore, a decrease of 4.0 x 10⁻¹⁹ J in the atom's energy corresponds to the emission of a photon with 4.0 x 10⁻¹⁹ J of energy.